Blood cancer treatments may one day include special dietary restrictions: researchers have found that an essential amino acid plays a crucial role in the creation of blood stem cells—a discovery the scientists say could lead to a potential alternative to chemotherapy and radiation.
Valine is one of 10 essential amino acids—protein building blocks that are crucial to life but cannot be made by the human body. It must therefore be obtained through diet and is found in protein-rich foods such as meat, dairy and legumes. Valine is involved in metabolism and tissue repair, and now it also seems key to the formation of blood stem cells. As reported in Science, researchers at the University of Tokyo and Stanford University found that human blood stem cells failed to proliferate when cultured in petri dishes without valine. Mice deprived of the amino acid for two to four weeks also stopped making new red and white blood cells.
Based on these results, senior author Hiromitsu Nakauchi and his colleagues think that depriving blood cancer patients of dietary valine before a bone marrow transplant might spare them the necessity of chemotherapy or radiation—both of which destroy cancer-causing blood stem cells to make room for transplanted ones but carry health risks. In a follow-up experiment, Nakauchi and his colleagues put the idea to the test in valine-restricted mice and were able to successfully transplant bone marrow without needing radiation or chemotherapy. But half of the mice died from a lack of valine shortly after the four-week trial ended.
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Nakauchi says it will take much more research to determine how long people can tolerate a valine-free diet (which would likely be supplied intravenously). But if the deprivation works in humans, it could open up the possibility of bone marrow transplants for some patients—such as pregnant women or people with low blood counts—who are usually not considered candidates for chemotherapy or radiation, says Linheng Li, a stem cell biologist at the Stowers Institute for Medical Research in Kansas City, Mo., who was not involved in the work. He suspects that this approach will need to be combined with other therapies or smaller doses of chemo and radiation to be effective, though.
Removing valine from the diet of certain leukemia patients could also potentially eliminate the cells that are the cause of their cancers in the first place, Nakauchi says: “If such a simple and relatively less harmful therapy could be used to treat leukemias, that would be great.”
